This invention relates to a mining machine for underground mining operations, and more particularly to a drumcutter type mining machine having a drive gearwheel with teeth in meshing engagement with teeth of a drive rack wheel that, in turn, drivingly engages a guide rail rack which extends along the course of travel by the mining machine.
A mining machine of this general type is disclosed in West German Pat. No. 2,543,510. In this prior art form of mining machine, the output shaft of winch on the mining machine carries a drive wheel having teeth which mesh with the teeth of a rack drive wheel which is, in turn, adapted to mesh with drive pins of a rail used for driving the mining machine along its course of travel. The guide rail comprises individual rail parts, each having a length which corresponds to the length of a conveyor trough portion of a face conveyor. The guide rail portions are mounted onto the stow side of the face conveyor. By this construction, the face conveyor and the guide rail are shifted together to carry out the usual advancement toward the working face of an underground mine. During the shifting operation, the individual conveyor trough portions together with the guide rail portions and more particularly those guide rail portions which are mounted on the stow side, are set at a greater or lesser relative angle. As a result, gaps are produced between the guide rail portions and these gaps cause pitch differences between the two driving pins of the guide rail portions which enclose the joint between them. This renders engagement of the drive rack wheel with the rack more difficult, particularly in view of the fact that the tooth flanks of the drive wheel have involute profiles which confer on the teeth a relatively compact shape and a low height. In view of this, the teeth of the drive rack wheel do not mesh with the rack in a manner to provide smooth running of the mining machine which is particularly impaired by the pitch differences occurring at the joints between the guide rail portions.